The Sava River has been defined as the main recharge source for the alluvial aquifers in its basin, especially in the upper part of the flow, in Slovenia and Croatia. However, there has not been a lot of research downstream of the Zagreb area which could show the magnitude of influence of the Sava River on the groundwater resources. This is mostly related to the area of Croatian and Bosnia and Herzegovina border, where in some parts the Sava River presents the border between two countries.

The aim of this project is to establish an international working group whose primary goal will be to establish new GNIP and GNIR points in the Sava River basin. Also, the research group will try to characterize groundwater-surface water interactions in the different parts of the Sava River basin, but also identify where the Sava River has more influence on groundwater resources. Evaluation of the isotopic results together with historical hydrological and meteorological data will show the influence of climate change on groundwater resources. All this will help to identify and implement measures for the sustainable groundwater resource management in the Sava River basin.